Oriented article having bead attached by tapered stem

ABSTRACT

The strength of the seal of an open end parison preform fabricated at orientation temperature is increased by forming a dependent bead within a closely adjacent longitudinal recess. In an alternate embodiment the appearance of seals is improved, and pin holes reduced by forming a dependent bead in a manner such that the longitudinal stem (web) connecting the bead flares outward adjacent a bottom wall of the article being molded.

ilnited States Patent Seefluth 5] Nov. 4, 1975 ORIENTED ARTICLE HAVINGBEAD 3,561,629 2/1971 Turner 215/1 0 ATTACHED BY TAPERED STEM 3,757,9789/1973 Gilbert 215/1 C [75] Inventor: Charles L. Seefluth, Bartlesville,

, Okla.

[73] Assignee: Phillips Petroleum Company,

Bartlesville, Okla. 22 Filed: Feb. 19, 1974' [2 1] Appl. No.: 443,473

Related US. Application Data [62] Division of Ser. No. 250,293, May 4,1972, Pat. No.

[52] US. Cl 215/1 C [51] Int. Cl. B65D 1/02 [58] Field of Search 215/1C; 220/66 [56] References Cited UNITED STATES PATENTS 3,417,892 12/1968Schweiger 215/1 C Primary ExaminerDonald F. Norton [57] ABSTRACT Thestrength of the seal of an open end parison preform fabricated atorientation temperature is increased by forming a dependent bead withina closely adjacent longitudinal recess. In an alternate embodiment theappearance of seals is improved, and pin holes reduced by forming adependent bead in a manner such that the longitudinal stem (web)connecting the bead flares outward adjacent a bottom wall of the articlebeing molded.

6 Claims, 10 Drawing Figures US. Patent Nov. 4, 1975 Sheet 1 of33,917,095

US. Patent Nov. 4, 1975 Sheet 3 of3 3,917,095

ORIENTED ARTICLE HAVING BEAI) ATTACHED BY TAPERED STEM CROSS REFERENCETO RELATED APPLICATION This is a divisional of copending applicationSer. No. 250,293 filed May 4, 1972 now US. Pat. No. 3,817,676.

BACKGROUND OF THE INVENTION This invention relates to sealing an openend parison at orientation temperature.

The blow molding art goes back for over one hundred years.Traditionally, blow molded articles have been formed by the downwardextrusion of a molten parison from an annular die into position betweenopposing mold halves. The mold halves have been closed and fluidpressure introduced into the parison to expand same into conformity withthe mold. Recently, techniques have been developed whereby high strengtharticles having exceptional sparkle and clarity can be produced by blowmolding a parison preform which has been cooled to room temperature andthereafter reheated to orientation temperature so as to achievemolecular orientation in the resulting article during the fabricationsteps. It is apparent that the most economical manner to produceindividual parison preforrns is to extrude a continuous length oftubular material and thereafter sever it into individual work pieces, asopposed to injection molding a closed end parison preform, for instance.However, this preferred method of forming individual parison preforrnscarries with it the inherent disadvantage of providing a preform whichis open at each end and which, therefore, must be closed at one endpreparatory to blow molding. Thus, in order to operate economically withindividual parison preforrns the artisan is faced with the problem ofachieving a seal in a parison which is at orientation temperature andthus far below the temperature at which the parison would be tacky andeasily sealable. It has been found that such preforrns can be sealedwith improved reliability by forming a dependent bead along the sealline. However, even with the dependent bead, the weakest point in theresulting bottle or other article is generally the seal area with thearticle generally failing along a line perpendicular to the seal line.That is, the seal does not break open but rather the bottom of thebottle on severe impact splits along a line perpendicular to thedirection of the seal. Also, on the inside of the bottle adjacent theseal line there is formed an area having voids and a generally roughappearance.

SUMMARY OF THE INVENTION It is an object of this invention to seal anopen end parison preform at orientation temperature;

it is a further object of this invention to provide an improved seal onparison preforms;

it is yet a further object of this invention to make possible theeconomic production of high strength, clear bottles having improvedseals; and

it is still yet another object of this invention to provide improvedapparatus for forming seals in parison preforrns at orientationtemperature.

In accordance with this invention an open end parison preform isstretched longitudinally after which the walls are sealed together andsevered to form a depending bead along the seal line within a closelyadjacent longitudinal recess. In accordance with an alternativeembodiment of the invention, a parison preform is stretchedlongitudinally after which the walls are sealed together in such amanner as to form a bead along the seal line connected to the bottomwall of the article being produced by a longitudinal stem which flaresoutward adjacent the bottom wall of the article being molded.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, forming a parthereof, wherein like reference characters denote like parts in thevarious views, FIG. 1 is a schematic representation of apparatus forforming and sealing parison preforrns in accordance with the instantinvention; FIG. 2 is an enlarged detailed section of sealing andsevering members in accordance with the invention; FIG. 3 is an enlargedsectional view of sealing and severing members in accordance with analternative embodiment of the invention; FIG. 4 is an enlarged sectionalview of sealing and severing members combining the features of FIGS. 2and 3; FIG. 5 is a view along section line 55 of FIG. 4; FIG. 6 is aview along line 66 of FIg. 4; FIG. 7 is a view of sealing and severingmembers having an alternative shape for the bead; FIG. 8 is a sectionalview of a bottle in accordance with the invention; FIG. 9 is a sectionalview of another bottle made in accordance with the invention; and FIG.10 is a bottom view of the bottle of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The parison preforrns which aresealed in accordance with the instant invention can be made from anyorientable material such as poly(vinyl chloride), polyesters, polymersof at least one mono-l-olefin having 2 to 8 carbon atoms per molecule,preferably polymers and copolymers of ethylene, propylene, and butene,more preferably polypropylene.

The open end parison preforms to be sealed in accordance with thisinvention can be formed by any means known in the art, although thepreferred means is to simply extrude a tube or pipe in a mannerconventional in the art and thereafter sever this continuous extrudateinto work pieces of the desired length.

The open end parison preforrns are heated to orientation temperaturepreparatory to sealing and blow molding. By orientation temperature ismeant that temperature at which polymers exhibit an increase in strengthon stretching. For crystalline polymers such as polymers ofmono-l-olefins having 2 to 8 carbon atoms per molecule, this temperatureis generally in the range of 1 to 50F, preferably 10 to 30F, below thecrystalline melting point. The crystalline melting point can bedetermined by placing a small sample of the material to be tested on aheating stage of a polarizing microscope and recording the crystallinemelting point as that temperature at last birefringence disappears onslow heating. The individual open end parison preforrns can be reheatedto this orientation temperature in an air oven, in a liquid bath, in aheating block, or by subjecting them to radiant heat, or any othersuitable means. For amorphous polymers a temperature of .40200,preferably l 50F below the homogeneous melt point is satisfactory.

In accordance with the invention the parison preform is stretchedlongitudinally and thereafter the sealing and severing members areclosed on a stretched portion thereof. Preferably, preblow fluid isintroduced into the interior of the parison to expand it slightly priorto the time the mold halves close on the stretched portion of theparison to seal and sever same. The longitudinal stretch ratio should bein the range of 1.1:1 to 8:1, preferably 1.5:1 to 25:1. By longitudinalstretch ratio is meant the ratio of the length of the parison to bestretched (i.e., the portion of the parison between the gripping means)after stretching to its length before stretching. A ratio of 111 wouldindicate no affirmative stretching prior to introduction of the blowfluid.

As noted hereinabove, it is highly preferred that the stretched parisonbe preblown slightly prior to closing the mold on it to effect sealing.This necessitates some means for temporarily closing off one end of theparison prior to the time the mold closes and forms the final seal. Itis preferred that this be done simply by grasping one end of the parisonwith a thread-forming means and the other end between two pinching meanswhich serve to close the parison off. The thread-forming means and thepinching means can then be moved axially apart to effect thelongitudinal stretch and fluid pressure can be introduced through ahollow mandrel in the thread-forming means with the escape of preblowfluid being precluded by the fact that the walls are closed together atthe other end thereof by the pinching fingers. Alternatively, a plug cantemporarily be placed in the open end of the parison or the open endcould be connected to the same source of preblow fluid as the other endso as to have fluid back pressure on the interior of the parison.

The preblow fluid must be introduced under a greater pressure than the 3to 6 psi normally used for preblowing in conventional blow moldingoperations in which hot extruded parisons are used. Preblow pressure ofat least 25 psig is preferred with a range of 25 to 50 psig beingentirely satisfactory.

The sealing and severing means has a severing edge which is thefurthermost extension thereof; this severing edge cooperates with amatching edge on the opposing mold half to sever the parison. Adjacent abottom wall-forming portion of the sealing and severing section of themold halves is a holding projection which cooperates with a matchingprojection on the opposing mold half to hold said thus severed parisonwithin a bead-forming mold to be described hereinbelow. Between theholding projection and the severing edge of each sealing and severingmeans is a relatively small cavity which, in cooperation with a matchingcavity on the other mold half, forms a bead-forming mold. Preferably,this bead mold generally has a circular configuration although otherconfigurations can also be used. This bead mold preferably has a maximumlateral dimension of to 25 percent of the combined thickness of the twowalls of the parison prior to stretching. For

I parisons having a wall thickness before stretching of 150 mils, amaximum lateral dimension of this bead mold of 45 to 75 mils issatisfactory.

As noted hereinabove, it has been found that articles sealed in thismanner tend to fail at what would appear to be the strongest point inthe entire article, that is, at right angles to the seal and an areawhich is generally several times thicker than the adjacent surroundingarea. Thus while the combination of a preblow and bead seal essentiallysolves the difficult problem of obtaining a sea] at orientationtemperature, there remains the problem of inadequate impact strength ina direction perpendicular to the seal in cases where the bottles aresubjected to unusually rough handling. Surpristhe seal line giving arough and unsightly appearance.

and in some instances actually resulting in pin holesi Surprisingly, ithas been found that if the stem connect ing the bead to the bottom wallof the article being molded flares slightly outward adjacent the bottomwall the appearance is improved greatly and the tendency to have pinholes is essentially eliminated. This phenomenon appears to defyexplanation although in light of the unexpected effectiveness of theprovisions for a slight flaring outward of the stem adjacent the wall itcan be speculated that the voids were caused in the first place by thesevering member in pressing against the outside wall of the parisoneffecting a cut on the inside wall.

In a preferred embodiment the recessed bead is used in combination withthe flared stem to give both a mechanically stronger seal and also amore reliable seal in that permeability is decreased because of thevirtual elimination of pin holes and/or thin areas along the seal 1line; in addition, the appearance is improved.

While it is not essential to the invention, it is preferred that thesealing and severing means have surfaces sloping back from the severingedge on the side opposite said bead-forming cavity at an angle such thatthe included angle of the opposed surfaces when the mold parts are in aclosed position is within the range of 15 to 100, preferably 25 to morepreferably 30 to 47. In this way, lateral pressure on the tail portionof the parison which is being severed has a vertical component of forcewhich is sufficient to cause the severed tail portion to fall free fromthe portion of the parison and held within the bead-forming cavity.

That portion of the mold which constitutes the sealing and severingmeans can be made of any suitable material. A preferred material is Vegasteel, hardened to a 59 to 60 Rockwell C hardness.

Referring now to the drawings, particularly FIG. 1, there is shown anextruder 10 for forming a tubular extrudate 12. Molten tubular extrudate12 passes immediately into vacuum cooling and sizing chamber 14.

The solidifed tubular extrudate then passes from sizing chamber 14 tocutting means 16 where it is severed into. individual open end parisonpreforms l8. Pan'son preforms ,18 pass through air oven 20 where theyare heated to orientation temperature. They are then transferred tothread-formin g head 22 by gripping fingers 24 which are broughttogether by means of air cylinders or cams, not shown. Thread-forminghead 22 can, for instance, be identical to that shown in Turner et al.,US. Pat. No. 3,390,426, the disclosure of which is hereby incorporatedby reference. Relative movement is then effected between thread-forminghead 22 having jaw means 23, and gripping fingers 24 by means of eitherraising gripping fingers 24, through the action of cylinder 25 whichserves as a means to effect relative axial movement, to the positionshown in FIG. 1 or else by means of lowering head 22 through the actionof an air cylinder, for example, not shown to stretch the parison I tothe elongated condition depicted by referenced character 18a. Preblowair is introduced through line 27. Mold halves 26 and 28 then close onthe thus stretched parison. Sealing and severing inserts 30 in moldhalves 26 and 28 perform the mechanical operation of bringing theparison walls into intimate contact and severing the parison as blow airis introduced through line 27 to inflate the parison.

FIg. 2 shows in detail sealing and severing inserts 30a in accordancewith one embodiment of the invention. Each insert has a severing edge 32which severs the parison along the sealing line. Surfaces 36,36 slopedownwardly and outwardly (in these figures the parts are disposed asthough the bottle were being blown right side up although as shown fromFIG. 1, the bottle can also be blown upside down which in many instancesis the preferred arrangement) from severing edges 32 to form an includedangle as shown in the drawing of about 47. Adjacent narrow bottomwallforming surfaces 38a, which form narrow longitudinal portions of thebottom of the article being molded, there are parison holdingprojections 40,40. In this figure each parison holding projection 40 hasa flat land area disposed parallel to the parting line of the mold asdepicted by reference character 42. As can be seen stem forming surface42 is adjacent an opposite edge of cavity 44 from edge 32. Smalllongitudinal bead-forming cavity 44 cooperates with a similar cavity inthe opposing insert to form a mold which forms a bead 46 connected withthe bottom wall 48 by means of longitudinal stem 49 (see FIG. 8). Member49 is referred to herein as a stem because in cross section it has theshape of a stem. Since it is longitudinal it is actually a web or tab.Bead 46 generally depends downwardly from lower surface 48 of the bottomwall section of the molded article a distance of to 400, preferably 25to 75, mils, that is, this is the height of stem 49. Of course, thiswill vary greatly depending upon the size of the parison being molded.Relative to the parison being molded, the height of the stem and beadwill generally be 0.1 to 3, preferably 0.3 to 1.3, times a single wallthickness of the parison before stretching. Stated in terms relative tothe size of the article being molded, the distance from severing edge 32to surface 38a will generally be 0.006 to 0.2, preferably 0.02 to 0.1times the average diameter of the bottom wall forming portion of themold. Generally the bottom of bead 46 will be just flush with surface 56(see FIG. 8) of the article. As above, the words downwardly, height,etc. are not meant to be limiting but are simply convenient descriptiveterms, it is being understood that the article can be upside down.

Viewing FIG. 2 in conjunction with FIG. 8, it can be seen that bead 46and stem 49 are formed within longitudinal recess 50 immediatelyadjacent thereto by means of upwardly projecting portions 52 of inserts30a. The width or lateral dimension of each flat top portion depicted byreference character 38a (and hence the width of the resulting recessadjacent the bottom wall of the article) on the inserts in FIG. 2(reference character 38 referring to the entire bottom wallforrningsurface) is about I to 150, preferably 25 to 75, mils although this willvary depending upon the size of the parison and will generally be in theneighborhood of 0.007 to l preferably 0.2 to 0.5, times the single wallthickness of the parison. Stated in terms relative to the size of themold, surface 38a will generally have a width of 0.004 to 0.06,preferably 0.01 to 0.04, times the average diameter of thebottom-forming portion of the mold. In some instances surface 38a may beup to 3 times as wide at the ends thereof as at the middle; in any eventthe above dimensions refer to the width in the middle, halfway betweenopposite ends of the bead.

Surface 38b then slopes down toward surface 38c which forms the bottomportion of the bottle. Thus, cavity 44, stem-forming surface 42, andnarrow bottom wall-forming surface 38a all project beyond adjacentgeneral bottom wall-forming surface 380. Surface 38b slopes primarily tofacilitate opening of the mold since the sloping surface allows thebottom of the bottle to be deflected inward as the mold opens.Surprisingly, this has the additional beneficial effect of counteractingthe normal tendency of a molded bottle to bulge outwardly at the bottom.Surface 38d simply forms that portion of the bottle around the peripherywhich normally comes in contact with the surface on which the bottle isplaced.

FIG. 10 shows a bottom view of bottle 55 of FIG. 8 showing bead 46within recess 50.

FIG. 3 shows an alternative embodiment of the invention wherein holdingprojections 40b slope back so as to form a stem which is flared adjacentthe bottom wall of the article being molded. As noted hereinabove, thissurprisingly prevents the polymer from being cut on the other side ofthe parison wall across from where the insert contacts the parison. Therelative dimensions of the bead-forming cavity and holding projectionsare otherwise identical to those described in FIG. 2, that is, thedistance from point 54 straight up to a point even with wall 38c wouldbe the same as the height of flat land 42 of the insert shown in Flg. 2.Surfaces 40b slope back from a line parallel with a parting plane of themold halves at an angle generally within the range of l to 25,preferably 10 to 20, degrees. Actually the significant dimension is therelative spacing between the holding projection at a point adjacent thebead and adjacent the bottom wall, with the gap adjacent the bottom wallgenerally being 1.5-4, preferably 22.5 times the gap adjacent the bead.Thus the further holding projections extend up the less the angle wouldbe. In this regard it must be emphasized that the speed at which thesealing and severing inserts close against the parison is a factor to beconsidered as the tearing which causes the voids referred to hereinaboveis greater if the inserts are closed very rapidly against the parison.If too much tearing occurs, the parison pops open and assumes itsinitial generally round configuration with the severed end being open.This matter is also interrelated to parison temperature, axial tensionon the parison, and the width of the gap between holding properties 40relative to the parison wall thickness. It must be kept in mind that theparison at orientation temperature exhibits elastic properties. If thetemperature is relatively low, i.e. just above that at which the polymerwill shatter, the parison is more likely to tear and. pop open.Specifically at temperatures just above where the polymer will shatter,closing times of 5 seconds or less will result in the parison poppingopen. Generally with a parison at orientation temperature the moldhalves will move at a speed sufficient to close in about 0.3 to 3,preferably 0.5 to 1, ,second although since it is the speed of closingthe final fraction of an inch that is important, this time could bereduced by closing rapidly at first and thereafter slowing the rate ofclosing.

In a fully closed position the gap between holding projections 40 (thatis, the width of the resulting stem 49) will generally be 25 to 100,preferably 45 to 60, mils, again depending on the thickness of theparison. Stated in terms relative to the thickness of the parison, thegap will generally be 20 to 55, preferably 30 to 40, percent of a singlewall thickness of the parison before 7 stretching. Especially goodresults are obtained utilizing a gap of 30 percent of a single wallthickness when preblow is utilized and 40 percent when no preblow isutilized. In connection with the width of the gap in instances such asin FIg. 3 where the stem varies in width minutes. The thus-heatedparisons were then placed in from the point adjacent the wall to thepoint adjacent thread-forming jaws such as are shown in FIG. 1 while thebead, the above described dimensions refer to the being held at theother end thereof by gripping fingers portronad acent the bead. Withconfigurations such as similar to those shown in FIG. 1. Relative axialmove shown in FIg. 5 (to be discussed hereinbelow) the ment was effectedbetween the said thread-forming above described dimensions are meant torefer to the means and said gripping fingers to achieve alongitudiportion in the center as opposed to the narrower pornal stretchratio of 2:1. Thereafter, preblow air at a tlons at the edges (but stillthe portion of the center adpressure of about 25 psig was introducedinto the inte- Jacent the bead). rior of the parison to give slightradial expansion to the Referring now to FIg. 4 there is shown in crosssecparison. Thereafter, mold parts similar to those shown tion inserts30c combining the features of FIGS. 2 and in FIG. 1 havingconfigurations in the sealing and sever- 3. As can be seen from FIG. 5,the configuration in ing area identical to that shown in FIG. 4 wereclosed FIG. 4 has the further feature of having a wider gap beupon theparisons. These operations were carried out in tween faces 42a,42a inthe center than at the ends. Also immediate succession so that theparisons remained at as shown in FIG. 6 face 42a has a greater height inthe orientation temperature. Main blow fluid at a pressure center thanat the ends. Faces 42a can have a short land of about 135 psig was thenintroduced into the interior area, i.e., area where opposing sides areparallel as of the parison to cause it to conform to the shape of theshown by reference character 43. This land can be up mold to give abiaxially oriented bottle having clear, to 30, preferably 5-25 percentof the total distance behigh strength walls. The resulting bottles werefilled tween edge 32 and surface 38a. with water and 10 bottles weredropped from a height.

FIG. 7 shows an alternative shape for the bead-formof 6 feet with thepercentage passing the 6 foot drop ing cavity 44a wherein longitudinalprojections or indibeing recorded. These tests were conducted at l, 7,14, vidual pins 56 are present. Because a polymer at orien- 21 and 28days. Results were as follows:

7: Bottles Passing 6-Foot Drop Melt Oven Temp. Bottle Age days FlowPinch Off F 1 7 14 21 28 3.50 Control 322 30 3o N.T.* 0 10 3.50Invention 322 100 100 100 N.T.* 100 3.05 Control** 321 90 N.T.* 100 so100 3.05 Invention 321 100 100 N.T.* 100 100 220 Control** 322 70 70 10070 70 2.20 Invention 322 100 100 100 100 100 1.08 Control** 322 so N.T.*100 90 80 1.08 Invention 322 100 N.T.* 100 100 100 0.87 Control**' 325100 100 N.T.* 100 100 0.87 Invention 325 100 100 100 N.T.* 100 0.81Control" 321 90 100 100 90 N.T.* 0.81 Invention 321 N.T.* N.T.* N.T.*100 100 Not Tested.

8 of 1.01-inch and a wall thickness of 0.165-inch. The tubing was cooledto room temperature in a vacuum sizing and quenching chamber and cutinto 5.75-inch lengths. These 5.75-inch lengths were heated for 40"Configurations similar to FIG. 3 except having flat parallel lands 42such as are shown in FIG. 2.

tation temperature is not readily moldable, provision for the members 57requires that cavity 44a be longer than circular bead cavity 44.

FIG. 8 shows a cross section of a bottle 55 made in accordance with theinvention and has been described hereinabove.

FIG. 9 shows a cross section of bottle 55a wherein bead 46a and stem 49aare within recess 50a but which differs from the configuration of FIG. 8in that the rest of the bottle bottom is entirely flat and the stemflares outward adjacent the bottom wall.

In the drawings, many conventional parts such as heaters, temperaturecontrollers, frames, cooling channels, and the like have been omittedfor the purpose of simplicity but their inclusion is understood by thoseskilled-in the art and is within the scope of the invention.

EXAMPLE I A series of polypropylene homopolymers having a density of0.905 (ASTM D 1505-63T), and various melt flows as determined by ASTM Dl238-62T, Condition L, and a crystalline melting point of about 340Fwere extruded into tubing having an outside diameter These data revealthat with the control pinch-off no more than 30 percent of the bottlesmade from 3.5 melt flow material passed the test. As the melt flowdecreases the bottles, of course, become better with to percent passingat 0.81 melt flow. However, with bottles made using the pinch-off of theinvention, 100 percent passed the test regardless of the melt flowwithin the range of melt flow tested.

EXAMPLE II Identical parisons were molded in an identical manner to thatof Example I except the sealing and severing member had essentially theconfiguration of FIG. 3, that is, the opposed faces of the membersbetween the bead forming cavity and the wall were tapered so as to givea wider stem adjacent the bottom wall of the article being manufactured,however, the stem and bead were not formed within a closely adjacentlongitudinal recess as in the invention runs of Example I. The oventemperature was 322F. One hundred percent of the bottles passed the6-foot drop test after 14 days of aging; however, only 50 percent passedafter 28 days aging. In a duplicate run, 90 percent passed after oneday, 80 percent after 2 days, 30 percent after 14 days and 50 9 percentafter 28 days aging. However, in both cases the bottles had improvedappearance and improved permeability characteristics due to the absenceof holes or thin areas on the seal area as compared with bottles made inan identical manner except with a sealing and severing member havingparallel opposed faces on the stem-forming holding projections likefaces 42 of FIG. 2.

CALCULATED ILLUSTRATIVE EMBODIMENT 1 Identical parisons to those used inExamples 1 and II are fabricated in an identical manner except thesealing and severing portions of the mold halves have the configurationshown in FIG. 2, that is, the facing surfaces of the sealing andsevering members have flat parallel configuration between the bottomwall-forming portion and the bead-forming portion with the entiresealing seam being formed in a closely adjacent longitudinal recess. Theresulting bottles have improved impact strength relative to bottles madeWithout the bead being formed in a closely adjacent recess, however, thebottles have a series of voids running along the seal line on the insideof the bottle.

While this invention has been described in detail for the purpose ofillustration, it is not to be construed as limited thereby but isintended to cover all changes and modifications within the spirit andscope thereof.

What is claimed is:

l. A bottle made of a thermoplastic material having a longitudinal beadconnected to a bottom wall of said bottle by means of a longitudinalstem which flares outward in a direction toward said bottom wall, adistance between said bead and said bottom wall being greater in thecenter than near the ends of said longitudinal bead.

2. An article according to claim 1 wherein opposed surfaces of said stemslope back at an angle of 1-25 from a line through said beadperpendicular to said bottom wall.

3. An article according to claim 1 wherein said bead and flared stem arewithin a narrow longitudinal recess.

4. An article according to claim 1 wherein said thermoplastic ispolypropylene.

5. An article according to claim 1 wherein said thermoplastic materialis biaxially oriented.

6. An article according to claim 1 wherein said thermoplastic materialis biaaxizllly |orieknted polypropylene.

1. A bottle made of a thermoplastic material having a longitudinal beadconnected to a bottom wall of said bottle by means of a longitudinalstem which flares outward in a direction toward said bottom wall, adistance between said bead and said bottom wall being greater in thecenter than near the ends of said longitudinal bead.
 2. An articleaccording to claim 1 wherein opposed surfaces of said stem slope back atan angle of 1*-25* from a line through said bead perpendicular to saidbottom wall.
 3. An article according to claim 1 wherein said bead andflared stem are within a narrow longitudinal recess.
 4. An articleaccording to claim 1 wherein said thermoplastic is polypropylene.
 5. Anarticle according to claim 1 wherein said thermoplastic material isbiaxially oriented.
 6. An article according to claim 1 wherein saidthermoplastic material is biaxially oriented polypropylene.